Investigate UntilImported in grandpa

## Issue summary

- Investigate the uses, determine priority, and come up with an implementation plan for UntilImported
- I do not think this is blocking for Import functionality, but it appears to be used in [round_data](https://github.com/paritytech/polkadot-sdk/blob/d18a682bf710fb3ce2ca21b186fb4e449e9ae857/substrate/client/consensus/grandpa/src/environment.rs#L774) as well as for grandpa global communication

## Other information and links

- Based on: https://github.com/paritytech/polkadot-sdk/blob/master/substrate/client/consensus/grandpa/src/until_imported.rs